Inhibitor



252. COMPOSITIONS,

pasta" ammo UNITED STATES (277 aw k RALPH E. LAWRENCE, OF WICKLIIFE, OHIO, ASSIGNOR TO THE GBASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF DELAWARE INHIBITOR llo Drawing.

This invention relates to processes of cleaning and pickling of metal articles by the action of acids thereon and is particularly directed to the use in the pickling and cleaning baths of certain organic substances which I found to have the property of inhibiting the action of acids upon the metal itself, without in any substantial manner impairing its ac- SNR, in which tion upon the oxide, rust, scale, salts or other undesirable incrustation which such operations are intended to remove from the metal. I found thathgustard oils, when added to dilute, non-oxidizin acids have these inhibiting properties. ustard oils are general- 1 ..scharacterized by having the formula R is a hydrocarbon radicalT 'Typical members of this group are allyl-mustard oil, phenyl mustard oil, toIyI- mustard eiknaphth'ylmustard oil, etc; The higher membersof' this class of substances, particularly those in which the hydrocarbon radical is of the aromatic series, are not very volatile and the small amounts needed to produce the inhibiting action in pickling and cleaning baths is insuflicient to produce any amount of obnoxious vapors which might preclude their use.

Pickling and metal cleaning operatlons involve commonly the use of dilute acids, such as sulfuric, hydrochloric, acetic, etc., or aqueous solutions of acid sulfates and such baths are used for numerous purposes of WhlCll pickling in steel mills and cleaning bfpipe lines are the most t ical representatives. The concentration arid composition of the bath, the temperature at which it is used and other factors vary of course in the different processes, though the underlyin comprises always the removal of t e undesirable incrustations b the action of the acid. The bare metal so 0 tained is then unavoidably subjected to the acid and attacked so that besides the desired cleaning efiect there is also quite a detrimental corrosion of the clean metal which evidences itself in the weakenin of the article and unnecessary consumption of acid. It has recently been shown that certain substances have the property of inhibiting the action of the acid upon the metal itself without impairing its action principle Application med October 9, 1929. Serial No. 898,570.

upon the incrustation and that this action is speclfic upon the hydrogen ion and quite in dependent of the anion of the acid bath, which in other words means that an inhibitor found efiicient with sulfuric acid will show similar inhibiting action with hydrochloric, acetic, or other non-oxidizing acids.

My novel inhibitors comprising the mustard oils are likewise efiicient with the various commonly used pickling and cleaning acids. The application of my invention to acid pickling and acid metal cleanin operations does not involve any substantia change in the baths and operation itself, except the addition of a small amount of inhibitors. Less than of 1% of a mustard oil added to an acid pickling or cleaning bath will to a large extent, if not entirely, prevent the attack of the metal under the conditions where all undesirable incrustations are removed. In some instances amounts of less than 0.1% are already efficient and sufiicient for all practical purposes. The use of my inhibitors in such operations results in a marked saving of acid and produces well cleaned articles free from pitting or brittleness, so commonly found in acid treated metallic articles.

Mustard oils being quite diflicultly soluble in dilute acids it is essential to have the same well distributed through the pickling and cleaning baths, and as these cannot be stirred efliciently I prefer to d i p e1; g my inhibitors through the bath by first djss o lying ihgm in stron acids or mix t "witfi'p'fotec 'tive 001101 I molasses-- residues, sulfonated vegetable oils, wetting agents, etc., such mixtures or solutions'when added to the dilute acids precipitate the inhibitor in finely divided form and render them much more heme. "Mm

The actual efiiciency of an inhibitor depends in large scale operations upon a number of factors and is rather diflicult to determine. It can, however, be determined comparatively by laboratory tests involving the measurement of gas evolved from a given surface of a piece of metal, immersed in a dilute acid containing the inhibitor. The less gas is evolved in a given time the more ef- 100 sub assulfite cellulose waste,

ficient is the inhibitor.

Amount of inhibitor added the bath 0 1% Hours of immersion 1 2 6! 1! 2' 6! 20 1 2 6 20 20 Allyl-mustard oil 0g 0 0; 23; 0? 0 0; 18 1 5 6 10 Phony! mustard oiL. 6 710 40 3j10 200 Tolyl mustard oi! a. 818 110; 655 1eo a= n Naphthyl mustard oil 12120 82 350'14 2 160 356 Same dispersed in 60 sul- I f I [uric acid T- i 0 0l 1 1 5I 8|54i 130 '25 A blank test made under the same conditions but without an inhibitor gave considerable more than 350 cc. of gas after 6 hours immersion.

My novel inhibitors are conveniently fur- 8 nished in the form of a solution, emulsion or admixture with a strong acid, a protective colloid, such as sulfite cellulose waste, molasses residue, etc., or with such diluting agent as desired and which will produce a complete dispersion of the active ingredient throughout the acid bath. All the pickler and cleaner has to do is to add such a composition to his standard acid bath and proceed in substantially the same manner as without my inhibitor.

I claim:

1. In a process of pickling and cleaning metal articles which comprises subjecting said articles to an acid bath containing as the active pickling and cleaning ingredient a nonoxidizing acid, the step of inhibiting the action of said acid upon the metal by the incorporation into the acid of an inhibitor comprising a mustard oil.

In a process of pickling and cleaning metal articles which comprises subjecting said articles to an acid bath containing as the active pickling and cleaning ingredient a nonoxidizing acid, the step of inhibiting the action of said acid upon the metal by the incorporation into the acid of an inhibitor com- :prising a mustard oil in fine dispersion throughout said acid bath.

3. A composition of matter for pickling and cleaning metal articles comprising a dilute, non-oxidizing acid and a small amount of an inhibitor comprising a mustard oil.

4. A composition of matter for pickling and cleaning metal articles comprising a While pickling opdilute, erations use acid concentrations of the order of an and temperatures fine di inhibitor comprising a non-oxidizing acidand a small amount mustard oil in stribution throughout the bath.

In testimony whereof, I aflix my signature.

RALPH E. L

AWRENCE. 

